dropping on a tree

[hubert fauque wanadoo fr]

Hello,
I am trying to drag (from another widget) and drop on a tree;
I have found that if I call drag_dest_set on the label
of the root_tree item I can drop an object on it, but it
doesn't work with the labels of the other items;
So, my question is: how to drop an object on a tree_item?

Thanks

Hubert